The present invention relates to immobilized microbial cells which are catalytically-active and to a method for preparing same in which the immobilization is effected by means of entrapping whole microbial cells or catalytically active biological material with a composition essentially comprising a polysaccharide containing glucuronic acid, rhamnose and glucose. Various techniques have been proposed for immobilizing microbial cells and enzymes on water-insoluble supports. These methods have included covalent chemical linkage to a support using functional groups of the enzyme that are not essential for enzymatic activity; entrapment of the microbial cell or enzyme within a hydrophilic gel lattice which retains the catalytically-active material while permitting substrate and product to pass through; ionic binding or physical absorption on hydrophilic ion exchange resins or on charcoal or glass beads and aggregating the enzymes by cross-linking with bifunctional compounds.
Entrapment methods of immobilization are most versatile. For example, U.S. Pat. No. 3,791,926 discloses methods of entrapping microbial cells and enzymes within polymer matrices U.S. Pat. No. 3,957,580 discloses a method of entrapping microbial cells within polymer systems in which the immobilized cells are further cross-linked to the polymer matrix using polyfunctional reagents such as glutaraldehyde.
However, synthetic polymer systems of the types described above have several drawbacks. The preparation of immobilized cells may involve the use of toxic materials such as monomers, initiators and cross-linkers linkers. The support matrix can deform or compress upon use in a commercial-scale bioreactor system.
Accordingly, it is the overall object of the present invention to provide a method of immobilizing, catalytically-active microbial cells which maintains enzymatic activity.
It is another object of the present invention to provide a method of immobilizing catalytically-active microbial cells which results in compositions exhibiting good mechanical strength.
It is still another object of the present invention to provide an immobilization method which results in compositions exhibiting kinetics comparable to soluble enzymes.
It is yet another object of the present invention to provide an immobilization method which uses an encapsulation polymer which is easy to use and inexpensive.
These and other objects and advantages will be evident from the following description and illustrative examples.